The present invention relates to a microwave-heating apparatus for irradiating microwave power to an animal to be tested in the biochemical field. In such an apparatus, enzymes in cells of the brain of the animal are inactivated in a moment by microwave irradiation.
Hitherto, there has been known, as shown in FIG. 1, method where a microwave power is generated from a magnetron 2 in a high-power microwave oscillator 1. The microwave power is transmitted through a circulator 3 and coupler 4, to be applied to an animal 6 in an applicator 5 for heating a brain of the animal 6.
The microwave power which has not been absorbed into the animal 6 returns to circulator 3, turns to an absorber in 7 at that place and then is absorbed to be absorber 7.
In such a microwave-heating apparatus, impedance matching is obtained by adjusting matching devices in a matching section 4 under high-power microwave output emitted from oscillator 1 for a standard test animal (e.g. a rat of 300 g). Thereafter, the matching section 4 is locked. Therefore, real matching cannot be performed for each specific animal put to use. This is because an impedance matching performed for each test animal would a harmful influence on the animal since the animal is heated with high-power microwave output supplied from the high-power microwave oscillator 1.
Though it might be possible to supply a low-power microwave output by means of lowering the power of the magnetron, a procedure for lowering the power of the magnetron is fairly severe. Besides, even if such a procedure is forcibly done, it causes a large energy loss.
In addition, the weight of an animal, taking as an example a rat, ranges from 100 g to 500 g. Therefore, the impedance matching state is varied at 100% to 80% in absorption factor. Moreover, even if rats of the same weight are employed, since the inserting states to the applicator 5 are different in every test, the absorption factor is varied further more. Therefore, it results in underheating or overheating of a rat. The latter case often results in destruction of the brain tissue of a rat and, as a result, poses an obstacle to the research.
On the other hand, the appropriate irradiation time (the term "irradiation time" means the time period of power irradiation required for obtaining the desired heating effect on a test animal) for heating a small animal, such as a mouse, is as short as 300 ms to 500 ms. However, the rise time of a microwave power (the term "rise time" means the time period required for coupling of the full radiated output power to the load) is conventionally 300 ms to 500 ms, that is to say, the irradiation time and the rise time are almost the same. Further, the microwave power does not exhibit constant value at every rise time, but rather it exhibits an unstable value.
Accordingly, the heating condition does not remain in a constant state, since the proportion of the rise time to the irradiation time is so great.
As described above, in a conventional microwave-heating apparatus, the impedance matching could not be obtained for every animal actually used. The heating condition could not be constant because the rise time of the microwave power was too long, so that repeatable data could not be obtained.
An object of the present invention is to provide a microwave-heating apparatus capable of heating a test animal in the same condition to obtain repeatable data.